Screening of antibacterial activity and phytochemical analysis of selected marine macroalgae from Hikkaduwa coast, Sri Lanka

Abstract

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Seaweeds are considered as a source of bioactive compounds as they are able to produce a great variety of secondary metabolites characterized by a broad spectrum of biological activities including antiviral, antibacterial, antifimgal and anticancer properties. The potentials of Sri Lankan seaweeds for the development of novel therapeutic agents remain unexploited. In this context, antibacterial susceptibility testing (ABST) of methanolic extracts of Padina antillarum, Caulerpa lentillifera, Sargassum sp. and Gracilaria corticata were conducted against two gram-positive {Staphylococcus aureus-ATCC 2593, Bacillus sp.) and two gram-negative {Escherichia coliATCC 25922, Pseudomonas aeruginosaATCC 2785) pathogenic bacteria by agar disc diffusion method. The extracts were subjected to qualitative phytochemical analysis. The crude methanolic extracts of P. antillarum showed an antibacterial activity against three out of four bacterial strains namely S. aureus (21.33±1.53mm), Bacillus sp. (21.33±0.58mm), P. aeruginosa (17.33±1.15mm) within 24 hours. The extract of C. lentillifera was found to be effective only against S. aureus (17.67±0.58inm) within 24 hours. There were no inhibitory effects detected for any o f the tested bacteria with the extracts of Sargassum sp. and G. corticata within 24 hours. The phytochemical analysis of the extracts revealed the presence of at least two phytochemicals among Alkaloids, Terpenoids, Flavonoids, Saponins, Tannins, Cardiac glycosides and Anthraquinones. The results of the present study showed the potential of seaweeds as a source of antibacterial compounds. Further studies are needed to carry out for the isolation and identification of the active compounds which can be chemical leads for the development of novel antibacterial agents